1. Priority Claim
This application claims the benefit of priority from Korean Patent Application No. P06-0011237 filed on Feb. 6, 2006 which is hereby incorporated by reference.
2. Technical Field
The present invention relates to a display device, and more particularly to a flat panel display device that is adaptive for improving picture quality by data modulation.
3. Related Art
Various flat panel display devices may have a reduced weight and size as compared to a display with a cathode ray tube. The flat panel display device may include various display panels such as a liquid crystal display, field emission display, plasma display panel, organic light emitting diode, and the like.
In some display devices, a picture quality defect can be identified when testing the display panel. The picture quality defect may include a panel defect (or mura defect), a bright spot caused by a defective pixel, a bright line caused by a backlight, and/or other visual imperfections.
A panel defect may cause a display spot which is seen to have a different brightness from an ambient screen. The display spot can have a shape of a dot, a belt, a block, a circle, a polygon, and/or other determined or undetermined forms. In some instances, a panel defect can occur because of a process defect and/or a lens number difference of an exposure machine. In some instances of a panel defect, when the same signal is applied to a defective panel area and a non-defective panel area, a picture displayed in the defective panel area is displayed darker or brighter than the picture displayed in the non-defective. In other instances, the color impression in the defective panel area and non-defective panel area can appear to be different. Panel defects may be generated in a fabrication process. Examples of panel defects having such various forms are shown in FIGS. 1A to 1E. A panel defect of a vertical belt is shown in FIGS. 1A to 1C and can be generated because of overlapping exposure and/or a difference in the number of lenses. A panel defect of a dot shape and an irregular shape are shown in FIGS. 1D and 1E, and may be generated by impurities. Due to the panel defect, Products may be condemned in accordance with the defect level, the defect of such products drops yield, and this leads to the increase of cost. Further, even when a product is found to have a panel defect but is shipped as a non-defective product, the picture quality can deteriorated due to the panel defect and the reliability of the product can decrease. Various methods have been proposed in order to improve the panel defects. However, these methods mainly address solving problems in the fabrication process.
A defective pixel on a display panel can be generated by a short circuit and/or wire breakage of a signal line, a defect of a thin film transistor (“TFT”), and/or an electrode pattern defect. The picture quality defect caused by a defective pixel can appear as a dark spot or bright spot in the display screen. Because the bright spot has a relatively greater degree of perception felt by the bare eyes as compared to a dark spot, the defective pixel appearing as the bright spot can be made darker so as to overcome the picture quality defect. Although a defective pixel made to be the dark spot, as shown in FIG. 2A, is almost not perceived in the display screen of the black gray level, the display screen of the middle gray level and white gray level, as shown in FIGS. 2B and 2C, there is a problem that the defective sub-pixel 10 made to be the dark spot is clearly perceived as a dark spot in the display picture even though the degree of perception felt by the bare eyes is low in comparison with the bright spot.
The bright line caused by the backlight the picture quality defect which can appear in the liquid crystal display device among various flat panel display devices. The liquid crystal display device, which is not a display device using a self luminous device, irradiates light to a rear surface of the display panel with a backlight, and controls the transmittance of light from the rear surface to the front surface so as to display a picture. The liquid crystal display device has a problem that the bright line appears on the display screen because the light from the backlight is not evenly incident to the whole incidence surface of the display panel. FIG. 3 represents an example of the bright line which mainly appears in the liquid crystal display device using a direct type backlight.